Over a very short period of time, vehicular simulators and especially flight simulators have developed from the early bellows driven LINK trainers to today's highly sophisticated, computer controlled flight mission simulators. With ever increasing versatility and fidelity, todays simulators duplicate a broad spectrum of flight conditions and aircraft performance of both normal and malfunction modes. By employing advanced motion systems, a multitude of digital computers, visual displays and the like, present day simulators are able to generate and integrate a multiplicity of realistic flight cues used to provide effective training for flight crew members. However, as will be appreciated by those familiar with the art of teaching, it has been found that the more senses of an individual that can be directed toward a problem the faster and more thoroughly he learns, Vocal communications and instructions have, of course, always been a primary mode of teaching. Means of providing such vocal instruction, has, of course, in the past typically been from an instructor who is monitoring the performance of the student pilot and who then provides information, instruction, etc., to the student on how to handle a particular flight situation. In addition, vocal communications are also used extensively with certain types of ground control approaches and the like where a monitor or ground controller on the ground talks "the pilot down" in a low visibility situation. It is seen that in vehicular simulation training, vocal or audio communications are still of primary importance. In prior art vehicular simulators, attempts have been made to record audio information and have the audio information played back in response to particular actions, failures or errors on the part of the student pilot. However, such audio information has in the past been recorded by means of audio tapes and disks or other techniques commonly used in vocal and sound recording. As will be appreciated by those skilled in the art, such analog recording techniques suffer from the inability of rapid response and the inability to continuously repeat information if needed continuously. That is, the time required to advance a tape to a proper location for a particular message, or to rewind a tape for replaying the message may be so time consuming as to be completely unsatisfactory.
Therefore, it is a principal object of the present invention to provide methods and apparatus suitable for reproducing stored vocal or audio information in a form providing for rapid and continuous availability of the information. It will be appreciated, of course, by those skilled in the art that certain various areas of the communication industry such as the telephone communication industry are already using digital techniques for vocal communications. These techniques include digitizing the vocal input, transmitting (by microwave or other means) the digital information, and then once the transmitted information is received at the proper location reconverting the digital information to an audio or vocal sound to be received by a user. Detailed information related to digital vocal techniques can be found in the following publications: "Automatic Voice Response" by L. H. Rosenthal et al, IEEE Spectrum pp 61-68, July, 1974; "A Multiline Computer Voice Response System Utilizing ADPCM Coded Speech" by L. H. Rosenthal et al IEEE Trans. Acoustics, Speech and Signal Processing, pp 339-352, Vol. 22, October, 1974; "Digital Representations of Speech Signals" by R. W. Schafer et al, Proceeding of the IEEE pp 661-677 Vol. 63, April 1975. However, none of the prior art systems include means as does the present invention for storing and making the instructional information available in vocal format upon command of a flight profile program for purposes of training and response to a student pilot's flying performance.
Therefore, it is a further object of the present invention to provide a mass digital storage system for digital audio playback apparatus.
It is a further object of this invention to provide an effective and inexpensive means for providing prerecorded audio information to a training simulator student or operation/instructor.
It is yet another object of the present invention to provide an audio playback instruction system having low power consumption.
It is yet another object of the present invention to provide an audio playback instruction system in which the audio instructions can be selectively edited.
It is still a further object of the present invention to compose audio messages from digitally encoded words and phrases.